Pressure swing recovery system for oil shale deposits

Abstract

A process for the in-situ recovery of hydrocarbon, carbon monoxide, and hydrogen values and associated minerals from subsurface oil shale deposits is provided by forming a gas-tight retort chamber and injecting it with various process gases which are pressure cycled over a predetermined period of time. This pressure cycling increases the extraction efficiency by improving the recovery of material contained in blind cracks in the underground formation, and by provising an independent means of controlling the thermal gradients induced in the deposit.

We claim: 
     
       1. A process for the in-situ recovery of hydrocarbon values and associated minerals from subsurface oil shale deposits in which a gas-tight retort chamber can be produced comprising the steps of: a. drilling into said oil shale deposits;   b. injecting steam into said shale deposits at varying pressures cycled over a predetermined time to dissolve and extract said associated minerals which are water soluble thereby forming a substantially gas-tight chamber;   c. injecting hot, non-oxidizing gas into said shale deposit at varying pressures cycled over a predetermined time in said chamber whereby said associated minerals are decomposed and hydrocarbon fluids extracted;   d. injecting a solvent-surfactant into said deposit at varying pressures cycled over a predetermined time and extracting said decomposed minerals and hydrocarbon fluids;   e. removing said solvent-surfactant from said deposit;   f. instituting a flame front and injecting air and water at varying pressures cycled over a predetermined time to combust hydrocarbon residue to produce liquid and gaseous hydrocarbons, CO, and H 2  ; and   g. filling said chamber with a fluid selected from the group consisting of water, aqueous solutions, and aqueous slurries.   
     
     
       2. A process according to claim 1 wherein said shale deposit is beneath a layered salt deposit. 
     
     
       3. A process according to claim 1 wherein said associated minerals are selected from the group consisting of nahcolite, dawsonite, nordstrandite, shortite, trona, and halite. 
     
     
       4. A process according to claim 1 wherein said pressure swings are ±35 percent of the ambient pressure in the well. 
     
     
       5. A process according to claim 1 wherein said predetermined time ranges from one cycle per minute to one cycle per day. 
     
     
       6. A process according to claim 1 wherein said water soluble mineral is selected from the group consisting of halite, trona, and nahcolite. 
     
     
       7. A process according to claim 1 wherein said hot, non-oxidizing gas is selected from the group consisting of low molecular weight hydrocarbon gas, carbon dioxide, carbon monoxide, hydrogen, nitrogen, steam, and mixtures thereof. 
     
     
       8. A process according to claim 1 wherein said solvent-surfactant is an aqueous solution of a compound selected from the group consisting of sodium carbonate and sodium bicarbonate and a surfactant selected from the group consisting of alkanol amines, alkanol amides, polyoxyethylene oxide block copolymers, carboxylic amides, carboxylic esters, ethoxylated aliphatic alcohols, ethoxylated alkylphenol, polyoxyethylenes, alkyl sulfates, N-acy-N-alkyltaurates, naphthalene sulfonates, alkyl benzene sulfonates, alkane sulfonates, alkanol amide sulfates, sulfated alkylphenols, and phosphate esters. 
     
     
       9. A process according to claim 1 wherein said decomposed minerals become chi-alumina. 
     
     
       10. A process for the in-situ recovery of hydrocarbon values and associated minerals from subsurface oil shale deposits in which a gas-tight retort chamber can be produced comprising the steps of: a. drilling at least one hole into the bottom of said shale deposit;   b. inserting piping to the bottom of said hole;   c. pumping steam down an injection pipe into said shale formation at varying pressures cycled over a predetermined time and extracting water soluble associated minerals from a producer pipe thereby forming a substantially gas-tight chamber;   d. injecting hot, non-oxidizing gas down said injection pipt into said shale deposit at varying pressures cycled over a predetermined time whereby said associated minerals are decomposed by heat and hydrocarbon fluids and are extracted from said producer pipe;   e. injecting a mixture comprising a surfactant and a portion of said water soluble mineral values previously obtained down said injection pipe at varying pressures cycled over a predetermined time and extracting said decomposed minerals and hydrocarbon fluids from said producing well;   f. clearing said chamber;   g. instituting a flame front and injecting air and water at varying pressures cycled over a predetermined time to combust hydrocarbon residue and extracting hydrocarbon values from said producer pipe for process heating;   h. filling said chamber with aqueous solution or slurry; and   i. raising the terminaton of said injector pipe and producer pipe a predetermined distance to begin the formation of the next gas-tight chamber in said shale deposit.   
     
     
       11. A process according to claim 10 wherein said shale deposit is beneath a layered salt deposit. 
     
     
       12. A process according to claim 10 wherein said associated minerals are selected from the group consisting of nahcolite, dawsonite, nordstrandite, shortite, trona, and halite. 
     
     
       13. A process according to claim 10 wherein said pressure swings are ±35 percent of the ambient pressure in the well. 
     
     
       14. A process according to claim 10 wherein said predetermined time ranges from one cycle per minute to one cycle per day. 
     
     
       15. A process according to claim 10 wherein said water soluble mineral is selected from the group consisting of halite, trona, and nahcolite. 
     
     
       16. A process according to claim 10 wherein said hot, nonoxidizing gas is selected from the group consisting of low molecular weight hydrocarbon gas, carbon dioxide, carbon monoxide, hydrogen, nitrogen, steam, and mixtures thereof. 
     
     
       17. A process according to claim 10 wherein said mixture is an aqueous solution of a compound selected from the group consisting of sodium carbonate and sodium bicarbonate and a surfactant selected from the group consisting of alkanol amines, alkanol amides, polyoxyethylene oxide block copolymers, carboxylic amides, carboxylic esters, ethoxylated aliphatic alcohols, ethoxylated alkylphenol, polyoxyethylenes, alkyl sulfates, N-acyl-N-alkyltaurates, naphthalene sulfonates, alkyl benzene sulfonates, alkane sulfonates, alkanol amide sulfates, sulfated alkylphenols, and phosphate esters. 
     
     
       18. A process according to claim 10 wherein said decomposed minerals become chi-alumina.